Polythioaminals (PTAs), a sub-set of polyaminals (PAs), may be produced by polymerization of hexahydrotriazines (HTs) with dithiols. The resulting polymers exhibit structurally dynamic behavior brought about by a chemical trigger (thiols). This structurally dynamic behavior is an attractive material property with potential application as therapeutic/drug conjugates, coatings, self-healing materials, reversible crosslinking materials, and as degradable hydrogels.
The synthesis of multifunctional PTAs of average molecular weights greater than 5000 grams/mole has been hampered by the current methods of PTA synthesis via HTs and dithiols. These methods and reaction pathway(s) involve the expulsion of volatile amine by-products (originating from the HT starting material), and which in turn has a negative impact on the reaction kinetics and thermodynamics. For example, it has been observed that as the molecular weight of the organic substituent bonded to the volatile amine by-product increases, the volatility of the amine by-product decreases, which results in a slower polymerization reaction and lower molecular weight PTAs (less than 5,000 gram/mole average).
To improve on the state of the art, there is a need for new synthetic schemes and pathways to functional PTAs and polyaminals (PAs) that bypass and do not depend on the formation and removal of volatile amine by-products. A useful new synthetic pathway is expected to yield PAs and PTAs of higher molecular weight and well defined architectures for expanded applications. It would be a further advantage to produce new PAs from multifunctional nucleophiles comprising heteroatoms other than sulfur, for applications intolerant of the odor of sulfur, and for those requiring oxidation resistant structures and functionality.